1. Field of the Invention
The present invention concerns a methacrylimide containing polymer of excellent transparency and heat resistance.
2. Description of the Prior Art
Methyl methacrylate polymers are excellent not only in transparency but also in weather proofness and mechanical property and, accordingly, they have been used as high performance optical plastic material and decorative materials. In recent years, their uses have been developed in the field of short distance light communication or optical sensors. However, since the heat-distortion temperature of methyl methacrylate polymers is as low as about 100.degree. C., they are not satisfactory for the use to applications requiring heat resistance and thus, there is a strong demand in the market for improving the heat resistance of methyl methacrylate polymers.
As a method of improving the heat resistance of a methyl methacrylate polymer, there has been proposed, for example, (1) a method of reacting a polymer of acrylic acid, methacrylic acid or an ester thereof with a primary amine, ammonia or a compound of forming a primary amine or ammonia in the presence of a solvent (refer to U.S. Pat. No. 2,146,209, German Patent Nos. 1077872 and 1242369), (2) a method of reacting a methyl methacrylate polymer with a primary amine in the presence of water (refer to U.S. Pat. No. 3,284,425) or (3) a method of reacting an acrylic polymer and ammonia or primary amine in an extruder (refer to U.S. Pat. No. 4,246,374).
However, in the method (1) described above, since the boiling point of the solvent used is high, it is difficult to completely separate the solvent from a resultant imidized polymer in a commercial scale and, as a result, the imidized polymer obtained is colored to reduce its transparency. In the method (2) described above, since reaction is conducted in the presence of water, methyl methacrylate segments suffer from hydrolysis in the case of intending to obtain a partially imidized polymer, making it difficult to obtain an imidized polymer having a desired heat resistance, as well as it is also difficult to perform uniform imidizing reaction. Further, in the method (3) described above, since the imidizing reaction is conducted between a polymer of high viscosity and a gaseous imidizing material, it is difficult to conduct a homogeneous imidizing reaction, making it difficult to obtain a homogeneously and partially imidized polymer.
Accordingly, although the heat resistance of the imidized polymers obtained by the methods described above is somewhat improved, since the transparency is poor, the molecular weight is substantially reduced, or imidization of the polymer is conducted only not-homogeneously upon commercial production, these methods have not yet been put to practical use at present.
An object of the present invention is to improve the foregoing drawbacks in the prior art and provide a methacrylimide containing polymer possessing properties such as excellent optical property, mechanical property, weather proofness and fabricability inherent in methacrylic acid ester polymers, and excellent in transparency and heat resistance.